1. Field of the Invention
The present invention is related to a rolling bearing unit with tone wheel which rotatably support a vehicle wheel with reference to the suspension apparatus while detecting the rotating speed of the vehicle wheel supported by this rolling bearing unit.
2. Description of the Related Art
A rolling bearing unit with tone wheel disclosed for example in JP Utility Model Publication KOKAI No. H5-27679 and JP Patent Publication KOKAI No. 64-21219 is known in the art to support a vehicle wheel with reference to the suspension apparatus while detecting the rotating speed of the vehicle wheel to control the antilock brake system (ABS) or traction control system (TCS).
The rolling bearing unit with tone wheel disclosed in the publication mentioned above is constructed as shown in FIG. 1.
There is a hub 1 having at its axially outer end portion (the widthwise outer end portion when installed in the vehicle, the left end portion in FIG. 1) an outer peripheral surface formed with a flange 2 to fix the vehicle wheel (not shown) to it.
The hub 1 has, at its intermediate portion, an outer peripheral surface formed with an inner ring raceway 3a, and at its axially inner end portion (the widthwise central side end portion when installed, in the vehicle; the right end portion in FIG. 5) an outer peripheral surface fitted with an inner ring 4 formed with an inner ring raceway 3b on its outer peripheral surface. The hub 1 and inner ring 4 form a rotating inner ring member or assembly.
Disposed on the outer peripheral surface of the stationary outer ring 5 is a mount portion 6 which supports the outer ring 5 to the suspension apparatus, and disposed on the inner peripheral surface of the outer ring 5 is a plurality of outer ring raceways 7a, 7b. Disposed between the outer ring raceways 7a, 7b and the inner ring raceways 3a, 3b are a plurality of rolling elements 8 to rotatably support the hub 1 on the inner side of the outer ring 5 which is supported by the mount portion 6 on the suspension apparatus.
Seal rings 9, 10 are fitted and secured to the opposite opening portions of the outer ring 5 such that the seal rings 9, 10 have inner peripheral edges in sliding or rubbing contact with the outer peripheral surface of the inner ring 4 and hub 1, respectively, so that rain water and muddy matter are prevented from entering the space inside the outer ring 5 where the rolling elements are installed.
As to the pair of seal rings 9, 10, the seal ring 9 on the axially inner side has a function of preventing the penetration of rain water and muddy matter, and a function as a tone wheel of detecting the rotating speed of the hub 1. Specifically, the seal ring 9 as shown in FIG. 2, is an assembly of the radially inner seal ring 11 fitted into the inner ring 4 rotating with the vehicle wheel, and a radially outer seal ring 12 fitted into the stationary outer ring 5.
The radially inner seal ring 11 is an assembly of a reinforcing metal 13a and seal member 14a of rubber or synthetic resin etc. while the radially outer seal ring 12 is an assembly of a reinforcing metal 13b and seal member 14b of rubber or synthetic resin etc. A reinforcing metal 13a has a circular ring portion 15a and a cylindrical portion 16a bent axially from the inner peripheral edge of the circular ring portion 15a while the reinforcing metal 13b has a circular ring portion 15b and a cylindrical portion 16b bent axially from the outer peripheral edge of the circular ring portion 15b. The cylindrical portion 16a is fitted onto the inner ring 4 while the cylindrical portion 16b is fitted into the outer ring 5 so that the seal rings 11, 12 are fixedly supported by the inner ring 4 and outer ring 5, respectively.
The seal members 14a reinforced by the reinforcing members 13a has peripheral edges in sliding or rubbing contact with the inner peripheral surface and side face of the mating reinforcing metal 13b, respectively. The seal members 14b reinforced by the reinforcing members 13b has a peripheral edge in sliding or rubbing contact with the outer peripheral surface of the mating reinforcing metal 13a. The seal between the outer peripheral portion at the axially inner end of the inner ring 4 and the inner peripheral portion at the axially inner end of the outer ring 5 is comprised of a plurality seal lips (three seal lips in the figure) to secure the sealing performance sufficiently.
In the reinforcing metal 13a fixedly fitted on the inner ring 4 rotating with the vehicle wheel, the circular ring portion 15a is formed with a number of through-holes 17 spaced apart from each other with a uniform space circumferentially. Accordingly, the magnetic property of the circular ring portion 15a is changed circumferentially alternately with a uniform interval, so that the circular ring portion 15a has a function as tone wheel.
A sensor 18 is supported by the non-rotating portion such as the suspension apparatus, and the detecting portion of the sensor 18 to detect the rotating speed is faced to the portion where the through-holes 17 are formed.
In the case of the rolling bearing unit with tone wheel as mentioned above, the vehicle wheel fixed to the flange 2 provided on the axially outer end portion of the hub 1, can be rotatably supported with respect to the suspension apparatus supporting the outer ring 5.
As the vehicle wheel rotates, the radially inner seal ring 11 fitted onto the inner ring 4 rotates, resulting in that the output of the sensor 18 opposed to the radially inner seal ring 11 changes. The frequency at which the output of the sensor 18 changes is proportional to the rotating speed of the vehicle wheel. Accordingly, the output signal of the sensor 18 is input to the controllers (not shown) to obtain the rotating speed of the vehicle wheel to suitably control the ABS and TCS.
In the case of the prior art rolling bearing unit with tone wheel as mentioned above, both of the radially inner and outer seal rings 11, 12 are provided with the seal member 14a, 14b, respectively. Therefore, the seal rings 11, 12 must be sufficiently cared during production and handling. Specifically, the seal member 14a supported by the reinforcing metal 13a of the radially inner seal ring 11 which functions as a tone wheel must be cared so that it is not damaged by muddy water splashing against it during the movements of vehicle. This is referred to as muddy water proof.
In addition, the seal members 14a, 14b of the seal rings 11, 12 must be sufficiently cared so that their peripheral edges or tip ends are not damaged during the time of period from the production to the assembling them between the outer peripheral surface of the inner ring 4 and the inner peripheral surface of the outer ring 5.
These cares will lead to cost-up of the rolling bearing unit with tone wheel having the radially inner seal ring 11.
In addition, the seal ring 9 installed in the rolling bearing unit with tone wheel can achieve a sufficient seal performance while the rotating speed of the vehicle wheel is detected, but unavoidably increases the production cost. Specifically, since the resilient members 14a, 14b are provided adjacent to the pair of reinforcing plate 13a, 13b of the seal ring 9, the production processes of the inner seal ring 11 and the outer seal ring 12 are so inconvenient to increase the cost of the seal ring 9 comprising the inner and outer seal rings 11, 12 in assembly.
In order to prevent such cost increase, the resilient member 20 as shown in FIG. 3, is attached to only the stationary seal ring 19 fitted and secured to the stationary ring such as the outer ring 5, and the resilient member 20 is provided with seal lips 21 in sliding or rubbing contact with the surface of the slinger 22 fitted and secured to the rotating ring such as the inner ring 4. In such a construction, however, no cutout such as through hole, notch could be formed in the portion of the slinger 22 with which the seal lips 21 are in sliding or rubbing contact, and therefore the function for tone wheel could not be achieved.
In order that the slinger 22 is provided with the function of tone wheel, the circular ring portion 23 of the slinger 22 is radially extended as shown in FIG. 4, and the cutouts such as notches 24 are formed circumferentially with a uniform interval on the tip half portion (upper half portion in FIG. 4) of the circular ring portion 23, so that the seal lips 21 are placed in sliding or rubbing contact with the base half portion (lower half portion in FIG. 4) of the circular ring portion 23.
However, in such a structure, the size in the radial direction of the circular ring portion 23 must be sufficiently large to secure the portion enough in size for sliding or rubbing contact with the seal lips 21, and a step portion 25 must be formed in the stationary ring such as outer ring 5 to avoid interference with the circular ring portion 23.
It is inconvenient to form the stepped portion 25 in the stationary ring made of a hard material such as bearing steel, leading to cost-up.